1. Field of the Invention
The present invention relates to a substrate treatment apparatus for treating a substrate with a hot chemical liquid. Examples of the substrate to be treated include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photo masks, ceramic substrates and substrates for solar cells.
2. Description of Related Art
Semiconductor device production processes include the step of locally implanting an impurity (ions) such as phosphorus, arsenic or boron, for example, into a major surface (front surface) of a semiconductor wafer (hereinafter referred to simply as “wafer”). In order to prevent the ion implantation into an unnecessary portion of the wafer, a resist pattern of a photosensitive resin is formed on the front surface of the wafer to mask the unnecessary portion of the wafer with the resist in this step. After the ion implantation, the resist pattern formed on the front surface of the wafer becomes unnecessary and, therefore, a resist removing process is performed for removing the unnecessary resist from the front surface of the wafer.
In a typical example of the resist removing process, the front surface of the wafer is irradiated with oxygen plasma to ash the resist on the front surface of the wafer. Then, a chemical liquid such as a sulfuric acid/hydrogen peroxide mixture (SPM liquid which is a liquid mixture of sulfuric acid and a hydrogen peroxide solution) is supplied to the front surface of the wafer to remove the asked resist. Thus, the resist is removed from the front surface of the wafer.
However, the irradiation with the oxygen plasma for the ashing of the resist damages a portion of the front surface of the wafer uncovered with the resist (an oxide film of the wafer exposed from the resist pattern).
Therefore, a method of lifting off the resist from the front surface of the wafer by the strong oxidative power of peroxosulfuric acid (H2SO5) contained in the SPM liquid supplied onto the front surface of the wafer without ashing the resist has recently been attracting attention.